Carbocatalysed Oxidative Csp2-Csp2 Homocouplings of Benzo-Fused Heterocycles

A1 Journal article (refereed)


Internal Authors/Editors


Publication Details

List of Authors: Tom Wirtanen, Mikko K. Mäkelä, Jawad Sarfraz, Petri Ihalainen, Sami Hietala, Michele Melchionna, Juho Helaja
Publisher: WILEY-VCH Verlag
Publication year: 2015
Journal: Advanced Synthesis and Catalysis
Volume number: 357
Issue number: 16-17
Start page: 3718
End page: 3726
ISSN: 1615-4169


Abstract

Appropriate and fine-tuned treatments of amorphous carbon (AC) involving aqua regia or concentrated HNO3 lead to oxidised carbon materials (oAC) which are able to catalyse 2,2′- and 3,3′-homocouplings of various functionalised indoles with outstanding activity. This newly developed carbocatalysed Csp2-Csp2 bond formation can be achieved under mild thermal conditions. The study on the scope of the reaction revealed that the reaction can be extended to the homocoupling of other substrates of high synthetic interest such as 2-naphthol, 2-functionalised benzofurans and benzothiofurans. The characterisation of oAC with XPS together with ad hoc experiments aimed at blocking the active site revealed that the presence and distribution of C=O functionalities is critical and correlates well with the catalytic activity. Such experiments provide solid support for elucidation of the mechanism, suggesting a quinone nature of the active C=O groups, which are spontaneously regenerated by oxygen. This is confirmed by the fact that 2,3-dichloro-5,6-dicyano-1,4-benzoquinone (DDQ) is able to promote the coupling in a stoichiometric fashion.


Keywords

heterogeneous catalysis

Last updated on 2019-17-08 at 05:00